Production of protein filaments



Patented Nov. 29, 1949 UNITED STAT EfS PATENT F :F ICE PRGDU'CTION OF PROTEIN \FILAMENYTS Walter Anderson Caldwell, West Kilbride, and Edwin Roberts Winton, Salt'cnats, Scotland, as-

' signers to Imperial Chemical industries Limited, a corporation of Great Britain No Drawing. Application May 16,"19 i'6,-'S'erial No. 610,034. In "Great Britain June 7, 1945 8 Claims. 1

ihe present invention is concerned with .an improved process for the production of protein filaments formed by extruding a solution of a vegetable globulin or casein in an aqueous solvent into an acidified saline coagulating bath, and is more particularly concerned with an improved process by which .the coagulated unhardened filaments are permanently extended in .length and reduced in cross-section, previous to the application of .an insolubilisation treatment.

It is known that by suitably stretching coagulated protein filaments so as to reduce their crosssection below that of the freshly .coagulated fllaments the tensile strength of the subsequently insolubilised filamentsis increased.

In a process for 'the manufacture of artificial threads, strips or hands :froman alkaline protein solution employing an acid spinning bath it has already been proposed inter alia. .to subject the freshly spun thread to a. continuous operation comprising treating the thread with one or more hot salt solutions and stretching it by means of a series of driven rollers or godets, the peripheral speed or" each roller or qgodet being greater than that of the roller or godet preceding it in the series, and the stretching of the thread taking place while it is in contact with the said hot solutions and thereafter hardening the thread with formaldehyde while it is in the untensioned condition. According to this proposal the freshly spun thread may be stretched while brought repeatedly into contact with one or more hot salt solutions, the temperature of the salt solutions being maintained @above 40' C. and preferably above 60 -C. At temperatures below 40 C. in aqueous saline solutions extension of the filaments is essentially recoverable when the tension is released, but as the temperature is increased the filaments exhibit increasingly thermoplastic properties, and the extension produced in the hot saline solutions retained when the tension is subsequently released.

The present invention provides a. method whereby the strength of the filaments may be more advantageouslyimproved,"and in particular a greater increase in strength achieved .for a given extension.

According to the present invention, therefore, the improved process for the production of filaments of vegetable globulins and casein by 2. stretching coagulated umhardened filaments obtained by ccagiulationin an acidifledesaline coagulating bath of :an extruded solution -;of ,a vegetable giobuiin .or casein comprises stretching said filaments in presence of :a saline solution having no swelling effect on them :and at a temperature not exceeding HP :and thereafter while maintaining them stretched subjecting them to the action of a hot saline solution at a temperature above 49 C. w'lriich has no swelling effect on the stretched filaments, they substantially retain their length when free from restraint and noionger in contact with said hot saline solution. last mentioned hotsolution may alsohave a dehydrating effect on the filaments,

The superior :gain .in strength for a given extension when the filaments :are treated zaccordm its the method of the present invention may be attribnted'to :the occurrence '.of an :intramolecular Lin-arrangement :under strain within the protein molecules individually when the filament is stretched in the presence :of the cold saline .solu-- tion having 'no swelling effect upon it and the of. :the stretched molecules in their rearranged condition with loss of strain when the filament is subsequently rendered thermoplastic by treatment in ;a saline bath at :a higher temperatiure above 40 It is believed fthaton the other :hand the filaments are stretched in comact with :hot saline solutions the extensionis mainly the resultlof :slip occurring between neighbourmgimolecu-lesloi thezprotein.

"Ilhe: ;process'.-accordingto the present invention is welzladaptedfor the continuous production of 1 protein filaments. capable :of subsequent hardening :or insolubilisation in the untensioned condition, since both the stretching. and the subsequent length fixation with thefhot saline solutionerequire so fiittle time that. these operations may desired be conducted while the filament is being continuously advanced after passing hroughthe.coagulatingzbath. Thestretch'mgof the coagulate-d protein filaments so :as to reduce: their 'c1foss:-seciiion below that of thefifreshly coagiileted material maybe carried-out in presence" of any convenient stronglyusaline aqueous solution, for instance the acidified saline solution of thercoagulating ibath It is unnecessary that the freshly coagulated filaments should be immersed in a bath of such solutions while they are being stretched, since they can be stretched in the air in presence of the liquid that adheres to them when they leave the coagulating bath or other suitable saline bath incapable of swelling them. The saline solution in presence of which the filaments are stretched may also have a dehydrating action on them and thus further reduce their cross section.

The hot concentrated saline solution in which the unhardened stretched filaments are subsequently treated may if desired contain a salt the same as that in the solution in presence of which they were stretched, but this is not essential. It may for instance be a salt that is present in a subsequent hardening or insolubilising solution in which the filament or fibre cut therefrom is treated.

If desired ingredients assisting the hardening or insolubilisation of the filament may be included in the hot saline solution.

The stretching of the filaments in presence of the saline solution having no swelling effect on the coagulated unhardened filaments carried out at a temperature not exceeding 40 C. and the subsequent subjection of the stretched filaments to the action of a hot saline solution at a temperature exceeding 40 C. may if desired be repeated as often as may be practicable.

The invention is illustrated by the following example, in which the percentages are by weight except where otherwise indicated.

A matured alkaline solution of peanut globulin is spun into a coagulating bath consisting of an aqueous solution containing 1.5 per cent sulphuric acid and 20 per cent sodium sulphate, from which the bundle of filaments emerging from a spinneret is withdrawn at a rate of 40 metres per minute, which is several times the linear speed at which the peanut globulin solution emerges from the holes in the spinnert. The continuous bundle is wound from the coagulating bath on to a swift from a godet in the coagulating bath, the swift being outside the bath and rotating at a winding speed of 52.5 metres per minute. Inasmuch as the swift is outside the bath, stretching takes place in the air in the presence of the adhering saline coagulating bath solution. The bundle of filaments passing round the godet in the coagulating bath is itself highly contractile, while the stretch on the bundle of filaments effected by the difference between the winding speeds of the swift and the godet is 31 per cent, the contractility of the bundle of filaments thereby being enhanced as a basis of comparison with the process of the present invention a bundle of the filaments having a length of 150 centimetres when stretched on a swift is cut soaked in saturated brine at 20 and subsequently insolubilised by immersing it in 20 times its dry weight of a bath consisting of a solution containing 2.5 per cent sulphuric acid, 1.5 per cent formaldehyde and 26 per cent sodium chloride for 20 hours at 35 C. and is subsequently washed and dried its length is found to be only 68 centimetres after soaking in saturated brine at 20 C., insolubilisation, washing and drying.

' The winding on the swift took 15 seconds in all. Stretched lengths of 150 centimetres each of the coagulated unhardened bundles of filaments are cut from the swift after it has been sprayed with a 20 per cent sodium sulphate solution at 45 C. for varying periods of time, and it is observed that the contractility of the filaments in Final length of Time of spraying with hot sodium sulphate solution Filaments 45 seconds centimetres. 90seconds 119 centimetres. seconds 123 centimetres.

The filaments treated with the hot sodium sulphate solution are of superior appearance and tensile strength.

We claim:

1. The process which comprises extruding a solution of at least one material of the group consisting of vegetable globulin and casein, in an aqueous solvent, into an acidified saline coagulating bath, collecting the resulting filament in a stretched condition by withdrawing it through said coagulating bath at a linear speed exceeding the linear rate of extrusion, then subjecting the collected filament to an additional stretch at a temperature not exceeding 40 C., while it is contacted by a saline solution (hereinafter referred to as solution A) having no swelling effect on it, and thereafter, while holding the filament thus additionally stretched, subjecting it to the action of a hot saline solution (hereinafter referred to as solution B) at above 40 C., said solution B also having no swelling effect on the filament.

2. The process of claim 1 wherein said solution A contains a salt the same as that in said saline coagulating bath.

3. The process of claim 1 wherein each of said solutions A and 13 contains a salt the same as that in said saline coagulating bath.

1. The process of claim 1 wherein at least one of said solutions A and B is approximately saturated.

5. The process of claim 1 wherein said additional stretch is applied at least partly in the air, and while said filament is contacted by liquid adhering to it in consequence of its withdrawal from said bath.

6. In the process of claim 1, the step of subjecting the filament, following said treatment at above 40 C. and while in untensioned condition, to an insolubilizing treatment.

'7. Theprocess of claim 1 wherein a hardening agent is present in said solution B.

8. In the process of claim 7, the step of subjecting the filament to a hardening solution containing said agent, subsequently to said treatment with solution B.

WALTER ANDERSON CALDWELL. EDWIN ROBERTS NINTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,358,427 Traill. Sept. 19, 1944 FOREIGN PATENTS Number Country Date 543,586 Great Britain Mar. 4, 1942 

